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LONDON — Like many teenagers, Harrison Killick likes to stay up late playing video games. But unlike most of his peers, Killick can play late even on a school night — because his school doesn't start until 11 a.m.

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The teen attends the Hugh Christie school in Kent county, southern England. For nearly two years, the school has been starting classes for 16-18-year-olds later than normal, with classes running from 11:00 a.m. until 5:00 p.m. And it is considering extending that policy to younger teenagers.

It is one of a handful of schools in Britain that delay class starts to midmorning. In the United States, schools or entire districts in 19 states have pushed back their start times. More than 100 school districts in 17 more states are considering delaying their start times.

As World Sleep Day is marked on Friday, many people may be wondering whether they get enough sleep. Since the Hugh Christie school began its experiment in 2006, 17-year-old Killick told AP Television News he feels much better rested and attentive in class.

"I feel a lot more relaxed and awake when I'm at school," said the teen, sporting a green polo shirt and earring.

Some experts believe that teenagers naturally need more sleep than adults.

"There's a change in hormones in teenagers' brains that requires some rewiring in the brain," said Jim Horne, director of the Sleep Research Center at Loughborough University. "That rewiring can only be done in deep sleep," he said, explaining that teens may need an hour more sleep than adults.

Delaying classes for teens until later in the day helps them learn better, experts say. Since classes were shifted later at the Hugh Christie school, average grades have improved.

But Horne worried that schools with later start times might also indulge teens. "It's possible this could be solved with better parental control," Horne said. "Is it really necessary for kids to stay up late every night chatting with their friends and in front of their computers?"

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